In order to generate 21cm maps from the EoR we used the publicly available semi-numerical code 21cmFAST v1.3 [1]}. The code generates Gaussian random initial density field and then evolves it using first order perturbation theory (Zel'Dovich approximation [2]}). In order to generate the \(x_{HI}\)  field, the code uses the excursion set approach pioneered by [3]}. In this approach a central pixel is marked as ionized if the evolved density field when smoothed at progressively smaller scales, starting at a maximum scale of \(R_{mfp}\)  meets the following condition for the ionizing efficiency \(\zeta \)  at some scale \(R\) :
\(f_{coll}(\mathbf {x},z,R) \ge \zeta ^{-1}.\) 
